It's all about that Base!

What is base training, is it necessary and what should it look like?

I think that for many athletes returning from an Autumn break, Winter is seen as a time for base training. However, I also think that for the majority, base training has come to mean slow endurance miles. This probably originates from the professional cycling ranks in which, historically at least, the off-season was viewed as a time to stay out of the big chainring and hit those long coffee shop rides. You’ve probably also heard the saying or seen the meme “Winter miles = Summer smiles” for instance. But does this still hold true? Below I have attempted to expand the concept of base training, explain it’s role and suggest some areas for you to consider when you are designing your base training or when viewing the work that your Coach has set for you.

Preparing a Foundation for Future Training

Firstly, if we consider base to mean ‘preparing a foundation for future training’ then base training could incorporate such things as developing the aerobic system, building muscular strength, improving certain aspects of technique and rehabilitating (also ‘prehabilitating’) an injury. What each individual triathlete actually requires and in what dosages is largely governed by their training history (both recent and past), their laboratory or field-testing results (benchmarks) and their future goals. In most cases the Coach will then devise a suitable plan to facilitate the base building process.

More generally speaking, base represents an athlete’s aerobic base. The ability to utilize oxygen in the metabolism of carbohydrates, fats and proteins to produce the energy required to exercise is the cornerstone of endurance sport. So, training should facilitate these metabolic processes. Now, before going any further let me just make a distinction. Is your goal to maintain an aerobic base or to progressively build an aerobic base? Remember that to develop any of our bodily systems we have to apply strain to signal the cells to adapt. Therefore, the long rides or runs that are synonymous with base building may actually only be sufficient to maintain your fitness. Now don’t get me wrong, maintenance of the aerobic system that you have built over the Summer may be all that is required for now. For instance, you may have other goals at the moment such as building muscular strength or power. Maybe you are looking to improve swim or run technique or perhaps you’re recovering from injury or illness. In all of these cases maintaining aerobic fitness may well be more appropriate than trying to build it. However, if you are looking to next year (a return to racing proper) and heightened performances then now may be the time to begin ‘building’ yourself a bigger aerobic base (see comments about having a bigger engine here!).

Does base building mean endless long, slow miles?

So, this brings us back to the original question “Does base building mean endless long, slow miles?”. There may be some merit in this approach, especially for the professional cyclist again, who has large amounts of time at their disposal. However, as the typical amateur triathlete doesn’t have such an abundance of free time, it becomes more important to question what the purpose of base training is and then by extrapolation consider how to best achieve that purpose. So how do we trigger positive adaptations within the aerobic system to make it stronger?

How do we trigger positive adaptations within the aerobic system to make it stronger ?

The benefits of aerobic training are highlighted in the table. It’s crucial to appreciate that any form of aerobic exercise will influence these adaptations in some way. Whether we train at an endurance effort level (Zone 2) or up to VO2max (Zone 5) the benefits are similar, only the magnitude of the stimulus changes. That is to say that all of the positive changes in the table will occur with progressive aerobic training but some respond more favourably at lower intensities and others at higher intensity levels.

In order to build that ‘bigger engine’ then, the simple fact is that, you will have to stress the aerobic system enough to trigger signals that will promote beneficial changes to be made. If you continue to do what you have become accustomed to, this may well maintain your base but is unlikely to build it. Practically that means you have to train progressively; consistently increasing duration and/or intensity. For example, a 2 hour zone 2 ride at the weekend is certainly not base building if you have been performing much longer or harder rides over the Summer. Same goes for a 90 minute endurance run, if you have been doing this and more too. In the example above your traditional base build would involve stretching those endurance durations (e.g. building the 2 hour ride into 4 hours or more), which in British Winter time is not often very appealing, even if we do have the time available. But surely there is another way….

Remember that all training zones below lactate threshold produce primarily aerobic benefits and even zones 4 (threshold) and 5 (VO2max) produce aerobic benefits in addition to some anaerobic ones. Therefore, when building your base, I feel you need to touch on the majority of the training zones and that this is also one of the times in the yearly cycle that it becomes more advantageous to spend some time for time crunched athletes, or those with a weakness in this area, at tempo 80-85% of FTP (Zone 3). This is a deviation from much of our typical training which is polarized (either easy or very hard with very little time spent in between) for a slightly more pyramidal approach (see below) for those who require it.

How can it be achieved

Including tempo rides and runs instead of monotonous endurance paced ones will allow stimulation of aerobic adaptations in a shorter time scale. Of-course the effort level just went up to make that happen but it means that you may be able to keep to a 2 hour ride time. It’s just that it now includes 1 hour of Zone 3 work (say 2x30mins) within it. As these efforts remain below lactate threshold and do not typically involve rapid movements or high load eccentric muscle contractions, recovery is usually reasonably quick and they can be repeated numerous times per week (if desired). Note also here that the descriptive terms of tempo and zone 3 are merely guidelines, this is particularly useful for those not on coaching plans and/or who have not undergone laboratory testing to establish their lactate profile.

For many athletes who have been to the lab or had discussions with their Coach, the substitution of a zone 3 effort for an upper Z2 effort may be more appropriate (*data from large cohorts of athletes suggests that LT1 (AKA- aerobic threshold; the point at which lactate levels first start to accumulate in the blood) occurs at approximately 75-77% of threshold on the bike. Unfortunately, it is much less predictable for running and is very difficult to measure when swimming. 75% remains at the upper end of your 2nd power training zone and 80% (tempo) which marks the lower point of your 3rd zone is just above this lactate turning point for many. Does this 5% really matter? Well to an extent it does. If we have accurate data for you as an individual we can prescribe these moderate efforts at the intensity that should work best for you and also allow you to recover quicker for the next session. For some 75% of FTP will be perfect and for others 80% (or even a little higher) would be better.

It may also be advantageous to perform intervals within the upper aerobic zones (4&5) in order to maximise your aerobic gains but the appropriateness and volume of this will need careful consideration at this time of year.

Some example sessions (not forgetting the possibility of touching all zones within a week)

  • Swap the 2 hour endurance ride in Zone 2 at 60-70% FTP for a 3-4 hour ride of similar intensity.
  • Add 90 mins at LT1 (75%) within the original 2 hours (e.g. 3x30mins)
  • Add 60 mins at tempo (80-85%) within the original 2 hour ride (e.g. 3x20mins).
  • Add time at sweet-spot (88-92%) cautiously but in the manner of 3x15 or 2x20.
  • Not forgetting that sessions above threshold such as threshold (Z4) or VO2max (Z5) add other aerobic stimulus and should not be overlooked
  • Another option is a progressive session in which the pace/power begins easy (Z1-2) and progresses over the duration towards threshold at the very end. This hits the majority of the zones and ensures that you both pace the session favourably and develop mental strength towards the end as the discomfort builds.


As usual you don’t get anything for free in endurance sports; every bit of fitness you gain, you have earned through hard graft. Long easy training sessions are not necessarily base building, nor is anything that is well within your comfort zone. If you’ve identified a Winter-time goal of building your aerobic base then focus in on those key aerobic training sessions and ensure that you increase the intensity or the duration where possible as you aim to progress. If you are short on time then it may be necessary to move to higher effort intervals but simply riding harder for an hour will not compensate for reduced duration. My personal approach would be to replace much of the time spent in easy zone 2 with blocks of effort in upper zone 2 and zone 3 (possibly up to sweet-spot and threshold on occasion). Finally, consider also that whilst triathlon involves 3 disciplines, aerobic adaptations have very good cross over from one to the others, so you do not have to suddenly start pushing forward on all fronts. Simply adapting one run and/or one bike per week as I’ve suggested above may be sufficient to stimulate those aerobic adaptations again.

By Phil Ellison: